Tooth replacement

ABSTRACT

The invention relates to a tooth replacement comprising at least one posterior tooth having a mesial contact surface, a distal contact surface, and an occlusal surface. The occlusal surfaces comprises a least one buccal cusp having a buccal cusp tip, a lingual cusp having a lingual cusp tip, a central fissure which has at least one tooth pit and passes through the occlusal surface in the mesiodistal direction between the two cusps, a first gradient which slopes downward from the buccal cusp tip in the direction of the central fissure, and a second gradient which slopes downward from the lingual cusp tip in the direction of the central fissure. The tooth replacement according to the invention is characterized in that the mesial contact surface, the distal contact surface and/or the occlusal contact surface comprise expansion spaces that have been incorporated in a targeted manner to obtain a dynamic occlusal guidance.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a 35 U.S.C. §371 national phase entryapplication of, and claims priority to, International Patent ApplicationNo. PCT/EP2012/002987, filed Jul. 16, 2012, which claims priority toGerman Patent Application No. DE 202011103184.9, filed Jul. 14, 2011,the disclosures of which are hereby incorporated by reference in theirentirety for all purposes.

BACKGROUND

The invention relates to a tooth replacement comprising at least oneposterior tooth having a mesial contact surface, a distal contactsurface, and an occlusal surface wherein the occlusal surface comprisesa least one buccal cusp having a buccal cusp tip, a lingual cusp havinga lingual cusp tip, a central fissure which has at least one tooth pitand passes through the occlusal surface in the mesiodistal directionbetween the two cusps, a first gradient which slopes downward from thebuccal cusp tip in the direction of the central fissure, and a secondgradient which slopes downward from the lingual cusp tip in thedirection of the central fissure.

Teeth are mainly used to crush food, but also to speak. The distinctivefeatures of a tooth include the crown that protrudes from the gum outinto the oral cavity, the tooth neck and the tooth root which may besplit and which at one end has an opening for nerves. The transitionbetween the tooth crown and the tooth root is referred to as the toothneck.

The natural dentition which consists of upper and lower jaw consists ofincisors, canine teeth and posterior teeth, i.e., the premolars andmolars. The premolars are built lower and feature a two-cusped crown,the molars have broad, up to 5-cusped crown.

In tooth replacements, artificial tooth crowns, entire replacement teethor full dentures to make sure of the masticatory function.

In the context of this invention, entire teeth and tooth crowns arereferred to as teeth.

Removable tooth replacement is necessary then when a large part of thenatural teeth is no longer present or even all teeth had to be removed.Today, such partial or full dentures mostly are made of plastic as asupport material, in which the replacement teeth are embedded.

The common replacement teeth which are implemented in simplified formoften cause unusual bite properties, wherein it is particularlyunpleasant that the temporomandibular joint responds even to smalldeviations from the usual movement sequence, and at times also it iselected not to use the dentures for extended periods of time.

As a solution to these problems in the prior art, EP 1 010 402 B1suggests a tooth replacement, wherein the replacement teeth are fittedwith multi-functional occlusal surfaces like their real lifecounterparts, have an enlarged volume and have a buccally stepped toothneck that prevents translucence of the tooth necks. Here, in thesesknown teeth, the cusps of the tooth crowns can have a slope thatdecreases from the premolars to the molars.

The disclosure of EP 1 010 402 B1 is hereby incorporated into thisdescription in terms of the formation of the occlusal surfaces and cuspslope by express reference. The use of the teeth as described in thecited document leads in many cases to satisfactory bite characteristics.However, it has been found that these bite characteristics may be lostduring the period of use of the known dentures.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawing:

FIG. 1 shows an embodiment of the tooth replacement according to theinvention from the front (FIG. 1 a) and from the back (FIG. 1 b),

FIG. 2 shows the occlusal surfaces of posterior teeth (molars andpremolars) of the tooth replacement according to the invention,

FIG. 3 shows side views of the left and right side of the jaw in the“neuronal contact position”,

FIG. 4 shows a view of the right half of the jaw from dorsal both in thephase of the closing of the jaw (FIG. 4 a) and in the closed position(FIG. 4 b),

FIG. 5 shows a view of the left half of the jaw from dorsal both in thephase of the closing of the jaw (FIG. 5 a) and in the closed position(FIG. 5 b),

FIG. 6 shows the occlusal surfaces of the posterior teeth of the toothreplacement according to the invention,

FIG. 7 shows an occlusal view, a lingual view and a basal view of atooth replacement according to the invention implemented in the form ofa row of teeth (second embodiment),

FIG. 8 shows further side views of the first embodiment of the toothreplacement according to the invention, and

FIG. 9 shows the occlusal surfaces of the individual posterior teeth ofthe first embodiment of the tooth replacement according to theinvention.

FIGS. 1 to 6, 8 and 9 show various views of a first embodiment of thetooth replacement according to the invention.

The expansion spaces that have been incorporated into the occlusalsurfaces in a targeted manner according to the invention can beparticularly clearly seen in the side views shown in FIGS. 3 to 5 and 8.

DETAILED DESCRIPTION

In view of the problems described in the prior art, the presentinvention seeks to provide an improved tooth replacement, which canensure the desired bite characteristics reliably over a long period oftime and which is established easily and clearly.

According to the invention this object is achieved by a refinement ofthe well-known tooth replacement that is essentially characterized inthat the mesial contact surface, the distal contact surface and/or theocclusal contact surface comprise expansion spaces that have beenincorporated in a targeted manner to obtain a dynamic occlusal guidance.

Advantageous embodiments of the invention are illustrated in thedependent claims.

Through the clear occlusal structure, the effective occlusion, andexpansion spaces that have been incorporated in a targeted manner, theposterior teeth can be easily and clearly established mutually. Inaddition, in the context of the invention, the teeth of the toothreplacement are fitted with natural occlusal surface dimensions. Here,the following features of teeth according to the invention are ofparticular importance:

-   -   a. Retrusion path    -   b. Smooth transition from the fissure guidance in the cusp        gradients (all degrees of freedom)    -   c. Protrusion path    -   d. Strongest support    -   e. Replacement tooth compliant    -   f. Stepped tooth neck    -   g. Approximal/interproximal contact surfaces    -   h. Functional alignment of the lock    -   i. Improved level of the central contacts    -   j. Special cusp slope

In the appended claims and the following explanation of the inventionuse is made of the following definitions:

-   -   Lingual cusps: include “inner cusps” of both the upper and the        lower jaw, i.e. lingual and palatal cusps    -   Buccal cusps: include “outer cusps” of both the upper and the        lower jaw    -   Transverse plane: sectional plane perpendicular to the tooth        axis    -   Frontal plane: sectional plane parallel to the tooth axis which        runs perpendicular to the mesio-distal axis of the tooth    -   Sagittal plane: sectional plane running parallel to the tooth        axis and in mesio-distal direction through the tooth    -   Posterior tooth: molar or premolar

The invention is based on the finding that an iatrogenic prostheticocclusion after incorrect bite produces an eccentric, i.e.,destabilizing condyle position or condyle displacement. For example, itwas recognized that an incorrect movement pattern, with the ultimategoal of maximum occlusion, is at the expense of the temporomandibularjoint, which cannot keep its own position rather leaves its position toadapt to the system.

In the context of the invention, “the neuronal contact position” on thetooth is the starting point and the endpoint for the expansion spacesthat have been incorporated in a targeted manner in the movement (thecourse of the occlusion). All movements on the occlusal surfaces aregently for the guidance of the temporomandibular joint in aphysiological position out of an effective central ICP and mean relieffor the entire system, including the joints.

The tooth replacement according to the invention allows all occlusionmovements to be performed perfectly. Here, use is made of the findingthat the centric jaw relation, i.e., the physiological mapping of thelower jaw to the upper jaw, is critical in all areas of prosthetics andhas a central importance for the success of the prosthetic restoration.

The tooth replacement according to the invention secures thisphysiological position of the temporomandibular joints in the ICP andthus of the stomatognathic system as a whole. The keys (right and lefttemporomandibular joints) find their correct occlusion position, fixedby the occlusal lock to the correct functional posterior teeth (FT). Inthe temporomandibular joint in conjunction with the neuromuscular systemthese will hold the keys in their desired position (physiologicalposition).

In the occlusal relief design of denture teeth, it is important not toreach a keyed point-to-point toothing, but to provide the patientthrough a small sliding clearance in the sense of a dynamic occlusionthe possibility of neuromuscular setting of his programmed physiologicaltemporomandibular joint centric.

The specifications for the design of tooth replacement according to theinvention were formed using an additive wax-up technique in a fullyadjustable articulator “type Protar”. Provisos from scientific studieshave been empirically implemented in a waxed mold and following firsttests to verify the required functional freedoms of the quadrantsdigitized in the laboratory and milled from PMMA plastic. This processallows the optimization of the occlusal surfaces according to scientificprinciples. In this context, a good centric allocation of jaw halvescontributes to fixing a healthy temporomandibular joint position.

In the context of the invention, in spite of all freedom, the closedrows of teeth provide secure centric support of the rows of teethagainst each other. The view onto the right jaw halves from dorsalclearly shows that both in the phase of the closing of the jaw as wellas mediotrusion movements the denture teeth function unimpededly.

The tooth replacement according to the invention was developed with thegoal of dynamic occlusal guidance in order to improve masticatoryperformance, stabilization of the prostheses, pleasant wearing comfortand reducing the risk of pressure sores, whereupon the special occlusionconcept has emerged. The movements on the tooth replacement according tothe invention run smoothly without interruptions, with correct setupinformation without grinding off, very evenly, both on the right and onthe side. It is possible to make restorations that are at maximum levelin term of functionality and aesthetics.

The tooth replacement according to the invention was obtained by thedevelopment and use of a system for measurement of jaw movements. Atooth replacement was created taking into account these scientificfindings. Scientific provisos have been empirically implemented in awaxed mold and following first tests to verify the required functionalfreedoms of the quadrants digitized in the laboratory and milled fromPMMA plastic. Using these prototypes measurements and tests have beenperformed and documented in a scientific experiment addressing thequestion of functionality in terms of the findings described. The dataand facts gained therefrom had an influence on a revision of theprototype and were then checked again. In doing so, the optimizationaccording to the invention of the occlusal surfaces was achievedaccording to scientific criteria.

According to a further aspect of the invention, the tooth replacementhas at least two adjacently arranged teeth, especially posterior teeth,of which one having a mesial contact surface can be contacted with adistal contact surface of another tooth, characterized in that themesial (distal) contact surface is curved convexly in a calotte-like orspherical manner, thus having a convex edge both in a sagittal plane andin a transverse plane, and the distal (mesial) contact surface is curvedconcavely spherically for producing a form-fit contact with the convexlycurved contact surface, thus having a concave edge both in a sagittalplane and in a transverse plane.

The mesial and distal contact areas that can be contacted are designedhave the shape of a spherical shell segment, so as to ensure form-fitcontact to one another in all tooth positions. On the one hand, thisenables the adaptation of the tooth replacement to the particularanatomy of the patient, on the other hand it produces a form-fit contactbetween adjacent teeth in the area of the mesial and distal contactsurfaces in all teeth positions, so that the desired anatomicallypredetermined position of the teeth can be reliably obtained. Theloosening of individual teeth in a plastic support which is occasionallyobserved in conventional tooth replacements is reliably excluded by thedevelopment of the mesial and distal contact surfaces according to theinvention.

In this context it has proved to be particularly advantageous if theradius of curvature of the convexly curved contact surface, whichpreferably is the mesial contact surface, is approximately equal to theradius of curvature of the concavely curved contact surface, saidconcave contact surface being preferably formed by the distal contactsurface.

Surprisingly, it has been found that the best possible anchorage of theteeth in the base material is achieved when the tooth neck of at leastone tooth is stepped in such a way that between crown and root arecessed shoulder is formed. Therefore, the tooth cross-sectiondecreases stepwise, starting from the tooth crown in the direction ofthe tooth root in the area of the tooth neck. The lower retention withlaterally acting forces caused by the stepwise reduction of the crosssection is more than offset, surprisingly, by the support of thetransition from tooth crown to the tooth root in the tooth area in thearea of the steps, so that overall improved anchorage of the tooth inthe base material is obtained. In addition, the translucence of thetooth necks through the plastic support is prevented by the steppedtooth neck.

In the context of the invention a recessed shoulder between the toothcrown and tooth root is understood to be a shoulder, which isconstituted that to a connection line between a boundary surface of thetooth root and the tooth crown in the area of the tooth neck extendsoutside of the tooth body.

A particularly reliable retention of the replacement teeth in thesupport material is achieved, when the shoulder between tooth crown andtooth root is implemented revolving around the entire periphery of thetooth, so that in the area of the transition between tooth crown andtooth root a circumferential contact face of the tooth is formed on thesupport material.

The invention can be used particular advantageously with entirereplacement teeth. The variability described in the adaptation ofreplacement teeth to the anatomical conditions of the patient can,however, already be achieved if crowns of adjacent teeth are implementedwith approximal contact surfaces, of which one is convexly curved andthe other is concavely curved for producing a form-fit contact. Theshape of the approximal contact surfaces for a tooth replacementaccording to the invention is optimized for a form-fit contact and thusincreased in comparison to the approximal contact areas of naturalteeth.

The circularly stepped dental neck used in a preferred embodiment of theinvention improves the fixing in the base and facilitates papillaedesign.

Hereinafter, the invention will be explained with reference to thedrawing to which express reference is made in respect of all detailsessential to the invention and which were not emphasized in more detailin the description.

The design of the occlusal surfaces of the posterior teeth of the toothreplacement according to the invention is illustrated particularly wellin FIGS. 2, 6 and 9.

The following features indicated in the claims are presented in thefigures: The fissure base is only relatively slightly curved. Thisresults in a smooth transition between gradients and central fissure. Inaddition, the base of the tooth pit is only relatively slightly curved.

The occlusal surfaces are continuously concavely curved in a frontalplane passing through the cusps starting from the first gradient throughthe central fissure to the second gradient. In other words, the centralfissure has no convex portions, so that in occlusion position no keyedpoint-to-point toothing is obtained, rather the patient is providedthrough a small sliding clearance in the sense of a dynamic occlusionthe possibility of neuromuscular setting of his temporomandibular jointcentric.

Furthermore, the gradients have no areas with steep slopes in thedirection of the cusp tips. This leads to a dynamic occlusion inlaterotrusion movements.

The central fissure has a minimum depth over the full tooth width. Thisleads to a dynamic occlusion in protrusion and retrusion. On the otherhand, the pit is not particularly deep in relation to the tooth width,which leads to the unimpeded functioning of the replacement teeth. Thedeepest point of the tooth pit is not the point of greatest curvature ofthe pit. In other words, the tooth pit is flat at the bottom. Thisfacilitates dynamic sliding movement starting from the occlusionposition.

FIG. 7 shows particularly clearly that the mesial contact surface oftooth 36 is implemented curved convexly so that it fits form-fit to thedistal contact surface of tooth 35. All teeth of the row of teeth ofFIG. 7 have a circumferentially stepped tooth neck, so that the toothcross-section decreases stepwise, starting from the tooth crown in thedirection of the tooth root in a shoulder implemented in the area of thetooth neck.

1. A tooth replacement comprising at least one posterior tooth having amesial contact surface, a distal contact surface, and an occlusalsurface, wherein the occlusal surface comprises a least one buccal cusphaving a buccal cusp tip, a lingual cusp having a lingual cusp tip, acentral fissure which has at least one tooth pit and passes through theocclusal surface in a mesiodistal direction between the two cusps, afirst gradient which slopes downward from the buccal cusp tip in adirection of the central fissure, and a second gradient which slopesdownward from the lingual cusp tip in the direction of the centralfissure, characterized in that the mesial contact surface, the distalcontact surface or the occlusal contact surface comprise expansionspaces that have been incorporated in a targeted manner to obtain adynamic occlusal guidance.
 2. The tooth replacement according to claim1, characterized in that the expansion spaces are implemented asprofilings extending in a normal direction to a tangent plane of thedistal contact surface, the mesial contact surface or the occlusalsurface.
 3. The tooth replacement according to claim 1, characterized inthat in a frontal plane passing through the central fissure the radiusof curvature of the occlusal surface at the base of the central fissureis greater than one quarter of a distance between the two cusp tips,resulting in a smooth transition between the first gradient, the centralfissure and the second gradient.
 4. The tooth replacement according toclaim 3, characterized in that in sectional planes running parallel to atooth axis through by a base of the tooth pit the radius of curvature ofthe occlusal surface at the base of the tooth pit greater than 1.2 mmand less than 4-5 mm.
 5. The tooth replacement according to claim 1,characterized in that the occlusal surface is continuously concavelycurved in a frontal plane passing through the cusps starting from thefirst gradient through the central fissure to the second gradient. 6.The tooth replacement according to claim 1, characterized in that in allfrontal planes passing through the central fissure, the maximum slopeangle of the first or of the second gradient with respect to atransverse plane is less than 40°, and more than 20°.
 7. The toothreplacement according to claim 1, characterized in that in all frontalplanes passing through the central fissure, a distance between the baseof the central fissure and the transverse plane passing through thehighest cusp tip is greater than 0.3 mm and smaller than 1.5 mm.
 8. Thetooth replacement according to claim 1, characterized in that a distancebetween the two cusp tips is more than 4 times and less than 15 times,than a distance between a transverse plane passing through the base ofthe tooth pit and a transverse plane passing through the highest cusp.9. The tooth replacement according to claim 1, characterized in that ina frontal plane passing through the base of the tooth pit the radius ofcurvature of the occlusal surface increases at least section-wisestarting from a base of the tooth pit in a direction towards an edge ofthe tooth pit.
 10. The tooth replacement according to claim 1,characterized by an antagonist of the posterior tooth having a furtherocclusal surface having at least one further cusp, which engages in anocclusion position with the tooth pit of the occlusal surface of theposterior tooth, wherein the length of the retrusion path starting fromthe occlusion position is at least 0.6 mm to 0.8 mm or the length of theprotrusion path is 0.4 mm to 0.6 mm.
 11. The tooth replacement accordingto claim 10, characterized in that in the occlusion position the cusp ofantagonist contacts the occlusal surface of the posterior tooth in thearea of the tooth pit in a planar manner, wherein the contact surface ismore than 0.5 mm² and less than 3 mm².
 12. The tooth replacementaccording to claim 1, characterized in that the distal or the mesialcontact surface is curved in a calotte-like or spherical manner, havinga convex edge both in a sagittal plane and in a transverse plane. 13.The tooth replacement according to claim 12 with an adjacent tooth ofthe posterior tooth having a further mesial or distal contact surfaceabutting the distal (mesial) contact surface of the posterior tooth,wherein the further mesial or distal contact surface of the adjacenttooth is curved concavely spherically for producing a form-fit contactwith the convexly curved distal or mesial contact surface of theposterior tooth respectively, having a concave edge both in a sagittalplane and in a transverse plane.
 14. The tooth replacement according toclaim 13, characterized in that the radius of curvature of the convexlycurved contact surface of the posterior tooth corresponds approximatelyto the radius of curvature of the concavely curved further contactsurface of the adjacent tooth.
 15. The tooth replacement according toclaim 1, characterized in that a tooth neck of the posterior tooth isoffset such between a tooth crown and a tooth root a recessed shoulderis formed, said shoulder revolving around a periphery of the posteriortooth.
 16. The tooth replacement according to claim 1, comprising atleast two adjacently arranged teeth, especially molars or premolars, ofwhich one having a mesial contact surface that is contactable with adistal contact surface of another tooth, characterized in that themesial or distal contact surface is curved convexly in a calotte-like orspherical manner, having a convex edge in a sagittal plane and in atransverse plane, and the distal or mesial contact surface is curvedconcavely spherically for producing a form-fit contact with the convexlycurved contact surface, having a concave edge in a sagittal plane and ina transverse plane.
 17. The tooth replacement according to claim 16,characterized in that the radius of curvature of the convexly curvedcontact surface corresponds approximately to the radius of curvature ofthe concavely curved contact surface.
 18. The tooth replacementaccording to claim 1, characterized in that the tooth neck of at leastone tooth is offset such that between a tooth crown and a tooth root arecessed shoulder is formed.
 19. The tooth replacement according toclaim 18, characterized in that the shoulder is implemented revolvingaround a periphery of the tooth.
 20. The tooth replacement according toclaim 1, characterized by an antagonist to one of the teeth, wherein thelength of a retrusion path from the tooth pit is 0.6 mm to 0.8 mm or thelength of a protrusion path from a neuronal contact position is 0.4 mmto 0.6 mm.